EP0310839B1 - A method of manufacturing monolithic integrated circuits - Google Patents
A method of manufacturing monolithic integrated circuits Download PDFInfo
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- EP0310839B1 EP0310839B1 EP88115210A EP88115210A EP0310839B1 EP 0310839 B1 EP0310839 B1 EP 0310839B1 EP 88115210 A EP88115210 A EP 88115210A EP 88115210 A EP88115210 A EP 88115210A EP 0310839 B1 EP0310839 B1 EP 0310839B1
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- reactor
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- deposition
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- 238000004519 manufacturing process Methods 0.000 title claims description 12
- 229910052782 aluminium Inorganic materials 0.000 claims description 19
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 19
- 238000000151 deposition Methods 0.000 claims description 16
- 230000008021 deposition Effects 0.000 claims description 16
- 238000000137 annealing Methods 0.000 claims description 13
- 238000011282 treatment Methods 0.000 claims description 13
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 12
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 claims description 9
- 238000000623 plasma-assisted chemical vapour deposition Methods 0.000 claims description 8
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 6
- 229910052757 nitrogen Inorganic materials 0.000 claims description 6
- 238000000637 aluminium metallisation Methods 0.000 claims description 3
- 229910052786 argon Inorganic materials 0.000 claims description 3
- 230000003247 decreasing effect Effects 0.000 claims description 2
- 238000011010 flushing procedure Methods 0.000 claims description 2
- 230000000977 initiatory effect Effects 0.000 claims 2
- XYFCBTPGUUZFHI-UHFFFAOYSA-N Phosphine Chemical compound P XYFCBTPGUUZFHI-UHFFFAOYSA-N 0.000 claims 1
- 238000002347 injection Methods 0.000 claims 1
- 239000007924 injection Substances 0.000 claims 1
- 238000000034 method Methods 0.000 description 23
- 235000012431 wafers Nutrition 0.000 description 15
- 229910052710 silicon Inorganic materials 0.000 description 13
- 239000010703 silicon Substances 0.000 description 13
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 12
- 238000001465 metallisation Methods 0.000 description 11
- 238000006722 reduction reaction Methods 0.000 description 10
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 9
- 230000009467 reduction Effects 0.000 description 9
- 238000006243 chemical reaction Methods 0.000 description 8
- 238000002161 passivation Methods 0.000 description 8
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 6
- 239000013078 crystal Substances 0.000 description 6
- 239000001257 hydrogen Substances 0.000 description 6
- 229910052739 hydrogen Inorganic materials 0.000 description 6
- 229910052814 silicon oxide Inorganic materials 0.000 description 6
- 229910052751 metal Inorganic materials 0.000 description 5
- 239000002184 metal Substances 0.000 description 5
- 229910021419 crystalline silicon Inorganic materials 0.000 description 4
- 239000000758 substrate Substances 0.000 description 4
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 3
- 239000004020 conductor Substances 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 239000011521 glass Substances 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 229910052698 phosphorus Inorganic materials 0.000 description 3
- 239000011574 phosphorus Substances 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 239000004065 semiconductor Substances 0.000 description 3
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- CSDREXVUYHZDNP-UHFFFAOYSA-N alumanylidynesilicon Chemical compound [Al].[Si] CSDREXVUYHZDNP-UHFFFAOYSA-N 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 239000012159 carrier gas Substances 0.000 description 2
- 238000005229 chemical vapour deposition Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000010354 integration Effects 0.000 description 2
- 238000011068 loading method Methods 0.000 description 2
- 230000007774 longterm Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 238000013508 migration Methods 0.000 description 2
- 230000001681 protective effect Effects 0.000 description 2
- 229910052581 Si3N4 Inorganic materials 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 1
- 238000010420 art technique Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 239000003989 dielectric material Substances 0.000 description 1
- 230000008030 elimination Effects 0.000 description 1
- 238000003379 elimination reaction Methods 0.000 description 1
- 125000004435 hydrogen atom Chemical group [H]* 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 230000008439 repair process Effects 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 229910000077 silane Inorganic materials 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 230000008646 thermal stress Effects 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
- H01L21/324—Thermal treatment for modifying the properties of semiconductor bodies, e.g. annealing, sintering
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/02104—Forming layers
- H01L21/02107—Forming insulating materials on a substrate
- H01L21/02109—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates
- H01L21/02112—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer
- H01L21/02123—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer the material containing silicon
- H01L21/02126—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer the material containing silicon the material containing Si, O, and at least one of H, N, C, F, or other non-metal elements, e.g. SiOC, SiOC:H or SiONC
- H01L21/02129—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer the material containing silicon the material containing Si, O, and at least one of H, N, C, F, or other non-metal elements, e.g. SiOC, SiOC:H or SiONC the material being boron or phosphorus doped silicon oxides, e.g. BPSG, BSG or PSG
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/02104—Forming layers
- H01L21/02107—Forming insulating materials on a substrate
- H01L21/02109—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates
- H01L21/02205—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates the layer being characterised by the precursor material for deposition
- H01L21/02208—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates the layer being characterised by the precursor material for deposition the precursor containing a compound comprising Si
- H01L21/02211—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates the layer being characterised by the precursor material for deposition the precursor containing a compound comprising Si the compound being a silane, e.g. disilane, methylsilane or chlorosilane
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/02104—Forming layers
- H01L21/02107—Forming insulating materials on a substrate
- H01L21/02225—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer
- H01L21/0226—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer formation by a deposition process
- H01L21/02263—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer formation by a deposition process deposition from the gas or vapour phase
- H01L21/02271—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer formation by a deposition process deposition from the gas or vapour phase deposition by decomposition or reaction of gaseous or vapour phase compounds, i.e. chemical vapour deposition
- H01L21/02274—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer formation by a deposition process deposition from the gas or vapour phase deposition by decomposition or reaction of gaseous or vapour phase compounds, i.e. chemical vapour deposition in the presence of a plasma [PECVD]
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
- H01L21/31—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to form insulating layers thereon, e.g. for masking or by using photolithographic techniques; After treatment of these layers; Selection of materials for these layers
- H01L21/314—Inorganic layers
- H01L21/316—Inorganic layers composed of oxides or glassy oxides or oxide based glass
- H01L21/31604—Deposition from a gas or vapour
- H01L21/31608—Deposition of SiO2
- H01L21/31612—Deposition of SiO2 on a silicon body
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S438/00—Semiconductor device manufacturing: process
- Y10S438/909—Controlled atmosphere
Definitions
- This invention relates to a method of manufacturing monolithic integrated circuits, particularly of the VLSI (Very Large Scale Integrated) CMOS (Complementary Metal Oxide Semiconductor) type.
- VLSI Very Large Scale Integrated
- CMOS Complementary Metal Oxide Semiconductor
- the structure of a monolithic integrated circuit basically comprises a small plate, or chip, of a semiconductor material wherein the various active and passive circuit components are formed.
- Such components are interlinked by a connection arrangement provided in a predetermined number of Link levels or planes which are isolated from one another by layers of a dielectric material.
- the first or innermost level in the structure is the so-called diffusion or junction level, and usually comprises a suitably doped substrate of crystalline silicon.
- the last level is referred to as the metallization level on account of it being formed by suitably shaping a layer of a metal, such as aluminum, in the proximities of the integrated circuit surface.
- the linking which is required to occur at a predetermined fixed signal voltage or "threshold" becomes the more critical to achieve as its size decreases, that is the larger becomes the integration scale of the integrated circuit.
- the latter is directed to ensure proper electrical operation at the links between the aluminum metallization level and the junction level of doped crystalline silicon by acting in a twofold way, that is by lowering the resistance of the aluminum-silicon contact, and at the same time reducing the residual valence forces present at the interface of the silicon crystal lattice.
- the aluminum annealing treatment process is carried out within tubular furnaces inside which a reducing medium (atmosphere of a forming gas composed of 95% nitrogen and 5% hydrogen) is maintained.
- a reducing medium atmosphere of a forming gas composed of 95% nitrogen and 5% hydrogen
- the presence of the aluminum metallization level poses, however, a top limit to the furnace inside temperature, which is to be maintained at a lower value than 450° throughout the process (whose overall duration is usually of 120 minutes).
- the temperature in each radial section of the furnace requires to be strictly controlled to a typical flat profile with a maximum allowable deviation of ⁇ 2°C.
- the hydrogen introduced into the furnace serves the function of reducing the residual valence forces present at the interface of the crystal lattice of the silicon forming part of the junction level.
- an unchanging prior teaching is to maintain within the annealing furnace a pressure not below atmospheric pressure.
- the passivation treatment is directed to confer on the circuits, by the deposition of a protective film thereon, adequate protection against the environment, as well as to ensure close adhesion of the metal conductors of the metallization level to the circuit, thereby preventing the electro-migration phenomenon.
- the protective film usually either silicon nitride or silicon oxide slightly doped with phosphorus, is deposited within reactors of the CVD (Chemical Vapor Deposition) type, consistently with a well-established technique.
- CVD Chemical Vapor Deposition
- a deposition reactor of the PECVD (Plasma Enhanced CVD) type may be a deposition reactor of the PECVD (Plasma Enhanced CVD) type.
- the standard operating conditions of such reactors provide for a temperature within the range of 300° to 380°C, a pressure around 133 Pa (1 Torr), and continuous feeding of a gas stream comprising SiH4, NO, PH3, and an inert gas, such as Argon with carrier gas functions.
- the deposition plasma is instead obtained as a rule by means of 400 kHz radio frequency supply.
- the whole deposition cycle including the steps of film deposition following loading and heating, and wafer cooling and unloading, lasts approximately 180 minutes, while the number of wafers that can be processed simultaneously within a conventional design PECVD reactor lies within the 100-unit range.
- an aluminum annealing process is known in the manufacture of a silicon device having a double-level metallization.
- an interlevel dielectric layer of silicon dioxide is deposited at a temperature not higher than 425°C and a pressure in the range of 26-53 Pa (0,2 - 0,4 Torr). It is believed that this heat treatment aids in alloying the first metallization layer onto the silicon substrate.
- the technical problem underlying this invention is to provide a method of manufacturing monolithic integrated circuits which can ensure for the largest possible number thereof proper and long-term stable electrical operation features, while overcoming the drawback affecting the prior art.
- performing the aluminum annealing and final passivation treatments under the claimed temperature and pressure conditions has surprisingly revealed an unexpected and improved activity of the hydrogen in reducing the residual valence forces which appear at the silicon crystal lattice interface.
- the above-noted aluminumannealing and final passivation treatments are applied inside a PECVD deposition reactor, owing to its ability to retain a constant temperature on its interior.
- the last-mentioned condition is, as will be recalled, a binding one for the aforementioned reaction (1) to take place as is typical with the aluminum annealing treatment.
- the method of this invention will afford, as a result, the following benefits: improved electrical yield of the circuits produced; and reduction in the overall manufacturing costs as brought about by savings in equipment (elimination of the aluminum alloying furnace), and reduction in the working time and clean room dedicated space requirements.
- the wafers were then subjected to pre-heating up to a temperature of about 250°C; the pressure inside the reactor was subsequently brought down to 200 Pa (1.5 Torr) while introducing at the same time a continuous stream of nitrogen at a volume rate of 2000 sccm (standard cubic centimeters per minute).
- the silane introduced into the reactor owing to the combined action of temperature and pressure, partly ionized to release hydrogen atoms to the surrounding medium.
- a reducing medium is created which, by virtue of the hydrogen produced diffusing through the various circuit levels, initiates a step of pre-reduction of the aforesaid residual valence forces.
- the passivating film deposition rate, its thickness and uniform doping were regulated by controlling the kinetics of the above-noted reactions by means of plasma provided by a 40 kHz radio frequency generator.
- the percent by weight of the phosphorus in the passivating film has been held below 3% to avoid corrosion problems with the circuits produced, as connected with the possible formation of phosphoric acid on their outer surfaces upon contact with the atmospheric humidity.
- the hydrogen required for carrying on the above reduction reactions is supplied directly to the reactor interior from the P-glass passivating film deposition reactions (2) and (3).
- the reactor On completion of the passivating film deposition step, which lasts about 30 minutes, the reactor was subjected to a flushing operation using a nitrogen stream at a flow rate of 2000 sccm for an about 30-minute time. Subsequently, the reactor was brought to atmospheric pressure, again using a nitrogen stream at 2000 sccm and for an about 11-minute time.
- the temperature was decreased gradually to a value of about 300°C, which is the same temperature as the wafers' on exiting the reactor.
- the boat is removed from the reactor and the wafers allowed to cool in air until room temperature is reached.
- the method according to the invention was then repeated, using the same procedures as specified above, on a like number of wafers containing double metallization level CMOS-KH2 and CMOS-KH3 circuits.
- CMOS-KH1, -KH2, and -KH3 integrated circuits as formed on a like number of wafers, were instead subjected to conventional aluminum annealingand final passivation treatments, respectively within a MINI BRUTE furnace (by Thermco) and a JANUS Model PECVD reactor (by Semy).
- the electrical yield EWS was then calculated from the above-mentioned electrical measurements.
- the method of this invention has led to achieving an advantageous outstanding increase in the electrical yield of the circuits produced, which increase shows to be 5.6% for the CMOS-KH1 circuits, 5% for the CMOS-KH2s, and as much as 9.5% for the CMOS-KH3s.
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Microelectronics & Electronic Packaging (AREA)
- General Physics & Mathematics (AREA)
- Manufacturing & Machinery (AREA)
- Computer Hardware Design (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- Power Engineering (AREA)
- Plasma & Fusion (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Formation Of Insulating Films (AREA)
- Electrodes Of Semiconductors (AREA)
- Metal-Oxide And Bipolar Metal-Oxide Semiconductor Integrated Circuits (AREA)
- Chemical Vapour Deposition (AREA)
Description
- This invention relates to a method of manufacturing monolithic integrated circuits, particularly of the VLSI (Very Large Scale Integrated) CMOS (Complementary Metal Oxide Semiconductor) type.
- As is known, the structure of a monolithic integrated circuit basically comprises a small plate, or chip, of a semiconductor material wherein the various active and passive circuit components are formed.
- Such components are interlinked by a connection arrangement provided in a predetermined number of Link levels or planes which are isolated from one another by layers of a dielectric material.
- The first or innermost level in the structure is the so-called diffusion or junction level, and usually comprises a suitably doped substrate of crystalline silicon.
- The last level is referred to as the metallization level on account of it being formed by suitably shaping a layer of a metal, such as aluminum, in the proximities of the integrated circuit surface.
- It is on this very metal layer that the contacts are formed for connecting the integrated circuit electrically to its surroundings.
- It is a well-known fact that monolithic integrated circuits are produced simultaneously and in large quantities from plates, better known as wafers, of some ordinary semiconductor material, usually crystalline silicon.
- The total number of the circuits to be formed on a single wafer increases proportionately with a so-called "integration scale".
- It should be noted that the peculiar methods of making integrated circuits, being as they are carried out on a microscopic scale, disallow subsequent repair of any faults of an electrical or mechanical nature developed incidentally during the various steps of the manufacturing course. It follows that a circuit is to be discarded at the slightest imperfection shown.
- Thus, in the manufacture of monolithic integrated circuits, there exists a basic need to ensure that the largest possible number of the circuits formed on each silicon wafer can operate successfully from the electrical standpoint.
- From the electrical standpoint, proper operation of an integrated circuit is tied to the method of linking the metallization level to the junction level.
- As is well recognized in the art, the linking, which is required to occur at a predetermined fixed signal voltage or "threshold", becomes the more critical to achieve as its size decreases, that is the larger becomes the integration scale of the integrated circuit.
- To meet the above-outlined requirement, it is current practice to resort to a treatment known by the term of "aluminum annealing or "aluminum sintering".
- The latter is directed to ensure proper electrical operation at the links between the aluminum metallization level and the junction level of doped crystalline silicon by acting in a twofold way, that is by lowering the resistance of the aluminum-silicon contact, and at the same time reducing the residual valence forces present at the interface of the silicon crystal lattice.
- It is recognized, in fact, that both said contact resistance and said residual valence forces affect in an uncontrolled way the value of the link threshold voltage between the metallization and junction levels.
- Investigation and reasearch work carried out on the matter have brought out that the objectionable influence of the aluminum-silicon contact resistance originates from the presence of a thin layer of silicon oxide (a few nanometers thick). This is regarded to form spontaneously due to the circuits being exposed to the atmosphere between the various steps of the manufacturing course.
- In accordance with a prior art technique, the aluminum annealing treatment process is carried out within tubular furnaces inside which a reducing medium (atmosphere of a forming gas composed of 95% nitrogen and 5% hydrogen) is maintained. The presence of the aluminum metallization level poses, however, a top limit to the furnace inside temperature, which is to be maintained at a lower value than 450° throughout the process (whose overall duration is usually of 120 minutes). Further, the temperature in each radial section of the furnace requires to be strictly controlled to a typical flat profile with a maximum allowable deviation of ±2°C.
-
- The hydrogen introduced into the furnace serves the function of reducing the residual valence forces present at the interface of the crystal lattice of the silicon forming part of the junction level.
- In order to enable diffusion of the hydrogen through the levels overlying said junction level, and consequently, its reaching the interface of the silicon crystal lattice, an unchanging prior teaching is to maintain within the annealing furnace a pressure not below atmospheric pressure.
- However, from an engineering and commercial standpoint, the so-called "useful life" of the circuits as obtained with the aluminum annealing technique is too short. This useful life is, as far as the electrical operating characteristics are concerned, shortened by such phenomena as electro-migration (a term used to designate an undesired transfer of matter inside the metal conductors of an integrated circuit) and corrosion. Accordingly, produced integrated circuits should be given high long-term operating stability features. According to techniques adopted heretofore, such features are imparted thereto by means of a treatment, known by the term of final passivation, which is applied subsequently to the aluminum annealing treatment and using procedures which are quite independent thereof.
- The passivation treatment is directed to confer on the circuits, by the deposition of a protective film thereon, adequate protection against the environment, as well as to ensure close adhesion of the metal conductors of the metallization level to the circuit, thereby preventing the electro-migration phenomenon.
- The protective film, usually either silicon nitride or silicon oxide slightly doped with phosphorus, is deposited within reactors of the CVD (Chemical Vapor Deposition) type, consistently with a well-established technique.
- Where deposition of a film of phosphorus-doped silicon oxide (or P-glass) is envisaged in which the phosphorus percent is to be controlled lower than 4%, at temperatures not to exceed about 400°C, of special interest may be a deposition reactor of the PECVD (Plasma Enhanced CVD) type.
- The standard operating conditions of such reactors provide for a temperature within the range of 300° to 380°C, a pressure around 133 Pa (1 Torr), and continuous feeding of a gas stream comprising SiH₄, NO, PH₃, and an inert gas, such as Argon with carrier gas functions. The deposition plasma is instead obtained as a rule by means of 400 kHz radio frequency supply.
- The whole deposition cycle, including the steps of film deposition following loading and heating, and wafer cooling and unloading, lasts approximately 180 minutes, while the number of wafers that can be processed simultaneously within a conventional design PECVD reactor lies within the 100-unit range.
- However, the manufacture of integrated circuits in accordance with prior methods has a number of drawbacks, and in the first place an undesired, and unavoidable, effect of mechanical damage to the circuits. This is a direct consequence of the reiterate manipulations to which the wafers are subjected and occurs on the occasions of the annealing furnace and passivation reactor loading and unloading operations.
- As a result of such mechanical damage, which generally shows up in the forms of breaks in the metallic conductors or breaks in the passivating film due to wafer scuffing, a decrease is suffered in the electrical yield of the circuits. In a known manner, this being the term used to indicate the ratio of the number of circuits operating properly from the electrical standpoint to the total number of the circuits processed.
- An additional drawback of significance is the high manufacturing cost of the circuits brought about by both the equipment cost and the cost of the dedicated space therefor in the so-called "clean room", as well as by the long times taken up by the need to first subject the integrated circuits to the aluminum annealing treatment and then to the final passivation treatment.
- From EP-A-225224 an aluminum annealing process is known in the manufacture of a silicon device having a double-level metallization. Subsequent to the deposition of a metal layer an interlevel dielectric layer of silicon dioxide is deposited at a temperature not higher than 425°C and a pressure in the range of 26-53 Pa (0,2 - 0,4 Torr). It is believed that this heat treatment aids in alloying the first metallization layer onto the silicon substrate.
- The technical problem underlying this invention is to provide a method of manufacturing monolithic integrated circuits which can ensure for the largest possible number thereof proper and long-term stable electrical operation features, while overcoming the drawback affecting the prior art.
- This technical problem is solved, according to the invention, by a method as defined in the appended claim.
- In accordance with the method of this invention, performing the aluminum annealing and final passivation treatments under the claimed temperature and pressure conditions has surprisingly revealed an unexpected and improved activity of the hydrogen in reducing the residual valence forces which appear at the silicon crystal lattice interface.
- In accordance with this invention, the above-noted aluminumannealing and final passivation treatments are applied inside a PECVD deposition reactor, owing to its ability to retain a constant temperature on its interior. The last-mentioned condition is, as will be recalled, a binding one for the aforementioned reaction (1) to take place as is typical with the aluminum annealing treatment.
- The method of this invention will afford, as a result, the following benefits:
improved electrical yield of the circuits produced; and
reduction in the overall manufacturing costs as brought about by savings in equipment (elimination of the aluminum alloying furnace), and reduction in the working time and clean room dedicated space requirements. - Further features and advantages of the inventive method will become more clearly understood by making reference to the following detailed description of a preferred, though not exclusive, embodiment thereof, to be taken by way of example and not of limitation.
- The various steps of the method according to this invention are carried out within a JANUS Model PECVD reactor by Semy whose design is quite conventional.
- A set including 100 silicon wafers, containing CMOS-KH1 circuits with a single metallization level, have been loaded in a boat and then introduced into the reactor. The wafers were then subjected to pre-heating up to a temperature of about 250°C; the pressure inside the reactor was subsequently brought down to 200 Pa (1.5 Torr) while introducing at the same time a continuous stream of nitrogen at a volume rate of 2000 sccm (standard cubic centimeters per minute).
- Steady pressure and temperature conditions were achieved after about 3 minutes. Then, the reactor inside temperature was gradually raised (within an about 10-minute time) up to a value of 450°C and held thereat with a maximum deviation of ± 2°C.
- Under this temperature condition, as controlled to a constant flat-profile value in each radial section of the reactor, the metallurgic reaction between the aluminum and the silicon oxide present in the link zones between the metallization level and the silicon substrate was started. In accordance with a characterizing aspect of the inventive method, in order to enhance the reduction of residual valence forces present at the crystalline silicon substrate interface, streams of SiH₄ and N₂ (as carrier gas) are admitted for an about 5-minute time into the reactor at volume rates of 168 and 2000 sccm, respectively.
- The silane introduced into the reactor, owing to the combined action of temperature and pressure, partly ionized to release hydrogen atoms to the surrounding medium. Thus, a reducing medium is created which, by virtue of the hydrogen produced diffusing through the various circuit levels, initiates a step of pre-reduction of the aforesaid residual valence forces.
- On completion of this pre- reduction step, the inflow of SiH₄ and N₂ was discontinued and the pressure inside the reactor further reduced to a value of 133 Pa (1 Torr). A fresh stream of gas comprising a mixture of SiH₄ (168 sccm), PH₃ (8 sccm), Argon (268 sccm), and NO (2200 sccm) was then fed into the reactor. Under these pressure and temperature conditions, the deposition of P-glass passivating film is started, and takes place in conformity with the following reactions,
- The passivating film deposition rate, its thickness and uniform doping were regulated by controlling the kinetics of the above-noted reactions by means of plasma provided by a 40 kHz radio frequency generator. In particular, the percent by weight of the phosphorus in the passivating film has been held below 3% to avoid corrosion problems with the circuits produced, as connected with the possible formation of phosphoric acid on their outer surfaces upon contact with the atmospheric humidity.
- According to the method of this invention, both the reduction of residual valence forces of the silicon crystal lattice and the metallurgic reaction of the aluminum with the silicon oxide at the links between the metallization and junction levels,proceed under the temperature and pressure conditions established within the PECVD reactor.
- Advantageously, the hydrogen required for carrying on the above reduction reactions is supplied directly to the reactor interior from the P-glass passivating film deposition reactions (2) and (3).
- It should be also noted that the typical reactions of the aluminumannealing process step take place in the absence of any interference from the plasma generated during the passivating film deposition.
- On completion of the passivating film deposition step, which lasts about 30 minutes, the reactor was subjected to a flushing operation using a nitrogen stream at a flow rate of 2000 sccm for an about 30-minute time. Subsequently, the reactor was brought to atmospheric pressure, again using a nitrogen stream at 2000 sccm and for an about 11-minute time.
- Concurrently with the pressure raising step, the temperature was decreased gradually to a value of about 300°C, which is the same temperature as the wafers' on exiting the reactor.
- Once atmospheric pressure is reached, the boat is removed from the reactor and the wafers allowed to cool in air until room temperature is reached.
- The method according to the invention was then repeated, using the same procedures as specified above, on a like number of wafers containing double metallization level CMOS-KH2 and CMOS-KH3 circuits.
- A second set of CMOS-KH1, -KH2, and -KH3 integrated circuits, as formed on a like number of wafers, were instead subjected to conventional aluminum annealingand final passivation treatments, respectively within a MINI BRUTE furnace (by Thermco) and a JANUS Model PECVD reactor (by Semy).
- On each circuit set, electrical measurements of a conventional kind were then taken to determine the number of the circuit operating correctly from an electrical standpoint of the total number of circuits produced.
- For each CMOS-KH1, -KH2 and -KH3 circuit type, as respectively produced with conventional aluminum annealing and final passivation treatments, and with the method according to this invention, the electrical yield EWS was then calculated from the above-mentioned electrical measurements.
-
- gross
- = overall number of circuits formed on a total of 100 wafers;
- good
- = arithmetical mean value, as calculated for a total of 100 wafers, of the number of devices operating correctly from the electrical standpoint;
- EWS
- = percent electrical yield = (good/gross) x 100.
- As brought out by the above chart, the method of this invention has led to achieving an advantageous outstanding increase in the electrical yield of the circuits produced, which increase shows to be 5.6% for the CMOS-KH1 circuits, 5% for the CMOS-KH2s, and as much as 9.5% for the CMOS-KH3s.
- It should be lastly noted that such an improvement in the electrical yield of the integrated circuits produced has been achieved by the inventive method thanks to the following combined factors:
improved reduction activeness on the residual valence forces of the silicon crystal lattice;
reduction in the faults induced incidentally in the circuits during their manipulation; and
lower thermal stress induced in the metallization level of aluminum.
Claims (1)
- A method of manufacturing monolithic integrated circuits having aluminum metallizations, comprising the following steps, carried out in sequence:- feeding said circuits into a PECVD deposition reactor;- providing, inside said reactor, an inert atmosphere controlled at a pressure in the range of 133-200 Pa (1-1.5 Torr), by a nitrogen stream infeed;- raising the temperature to a value of up to 450°C but greater than 420°C and injecting a stream of SiH₄ and N₂, thereby initiating an aluminum annealing treatment;- discontinuing said injection of SiH₄ and N₂ after a predetermined time period;- setting the pressure to a value of about 133 Pa (1 Torr);- initiating, while continuing aluminum annealing, a deposition of a passivating film by feeding a stream of SiH₄, PH₃, Argon and NO, simultaneously generating a deposition plasma therefrom;- flushing the interior of said reactor by feeding a nitrogen stream; and- unloading, at the end of a predetermined time period, said circuits from said reactor after the pressure has been raised to atmospheric and the temperature decreased to about 300°C.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
IT8722216A IT1231887B (en) | 1987-10-09 | 1987-10-09 | PROCEDURE FOR THE PRODUCTION OF MONOLITHIC INTEGRATED CIRCUITS |
IT2221687 | 1987-10-09 |
Publications (2)
Publication Number | Publication Date |
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EP0310839A1 EP0310839A1 (en) | 1989-04-12 |
EP0310839B1 true EP0310839B1 (en) | 1995-11-22 |
Family
ID=11193182
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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EP88115210A Expired - Lifetime EP0310839B1 (en) | 1987-10-09 | 1988-09-16 | A method of manufacturing monolithic integrated circuits |
Country Status (5)
Country | Link |
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US (1) | US4920077A (en) |
EP (1) | EP0310839B1 (en) |
JP (1) | JPH02313A (en) |
DE (1) | DE3854710T2 (en) |
IT (1) | IT1231887B (en) |
Families Citing this family (7)
Publication number | Priority date | Publication date | Assignee | Title |
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US5432128A (en) * | 1994-05-27 | 1995-07-11 | Texas Instruments Incorporated | Reliability enhancement of aluminum interconnects by reacting aluminum leads with a strengthening gas |
US5514628A (en) * | 1995-05-26 | 1996-05-07 | Texas Instruments Incorporated | Two-step sinter method utilized in conjunction with memory cell replacement by redundancies |
US6013584A (en) * | 1997-02-19 | 2000-01-11 | Applied Materials, Inc. | Methods and apparatus for forming HDP-CVD PSG film used for advanced pre-metal dielectric layer applications |
US6073576A (en) | 1997-11-25 | 2000-06-13 | Cvc Products, Inc. | Substrate edge seal and clamp for low-pressure processing equipment |
US6350673B1 (en) * | 1998-08-13 | 2002-02-26 | Texas Instruments Incorporated | Method for decreasing CHC degradation |
WO2001078126A2 (en) * | 2000-04-07 | 2001-10-18 | Philips Semiconductors, Inc. | A method of passivating a metal line on a wafer |
DE10114764B4 (en) * | 2001-03-26 | 2005-08-11 | Infineon Technologies Ag | A method of fabricating an integrated circuit with a dynamic memory cell array (DRAM) having a long retention time |
Family Cites Families (7)
Publication number | Priority date | Publication date | Assignee | Title |
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GB2058731A (en) * | 1979-09-12 | 1981-04-15 | Philips Electronic Associated | Method of making semiconductor devices |
US4380115A (en) * | 1979-12-06 | 1983-04-19 | Solid State Scientific, Inc. | Method of making a semiconductor device with a seal |
JPS5957458A (en) * | 1982-09-27 | 1984-04-03 | Fujitsu Ltd | Manufacture of semiconductor device |
JPH071764B2 (en) * | 1984-06-01 | 1995-01-11 | テキサス インスツルメンツ インコ−ポレイテツド | Method for manufacturing semiconductor device |
JPH0622234B2 (en) * | 1984-07-20 | 1994-03-23 | 富士通株式会社 | Method for manufacturing semiconductor device |
JPS61212025A (en) * | 1985-03-18 | 1986-09-20 | Hitachi Ltd | Forming method for phosphorus silicate glass (psg) film |
EP0225224A3 (en) * | 1985-10-29 | 1987-11-19 | Thomson Components-Mostek Corporation | After oxide metal alloy process |
-
1987
- 1987-10-09 IT IT8722216A patent/IT1231887B/en active
-
1988
- 1988-09-16 EP EP88115210A patent/EP0310839B1/en not_active Expired - Lifetime
- 1988-09-16 DE DE3854710T patent/DE3854710T2/en not_active Expired - Fee Related
- 1988-09-27 US US07/249,788 patent/US4920077A/en not_active Expired - Lifetime
- 1988-10-07 JP JP63252237A patent/JPH02313A/en active Pending
Also Published As
Publication number | Publication date |
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IT1231887B (en) | 1992-01-15 |
DE3854710T2 (en) | 1996-08-01 |
JPH02313A (en) | 1990-01-05 |
IT8722216A0 (en) | 1987-10-09 |
US4920077A (en) | 1990-04-24 |
EP0310839A1 (en) | 1989-04-12 |
DE3854710D1 (en) | 1996-01-04 |
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